Plasma source and plasma processing apparatus

ABSTRACT

A plasma source ( 1 ) is composed of a chamber ( 2 ) to which a gas should be supplied and a hollow cathode electrode member ( 4 ) which is arranged on the gas flow-out side of the chamber ( 2 ) and has a plurality of electrode holes ( 3 ) through which the gas can flow. In such a plasma source ( 1 ), microcathode plasma discharge can be performed in the electrode holes ( 3 ) of the hollow cathode electrode member ( 4 ).

TECHNICAL FIELD

The present invention relates to a plasma source and plasma processingapparatus which enable highly efficient plasma generation.

BACKGROUND ART

The present invention can be widely and generally applied to themanufacture of the material of a semiconductor or an electronic devicesuch as a semiconductor device or liquid crystal device, and will bedescribed exemplifying the background art of the semiconductor devicefor descriptive convenience.

In recent years, as the integration density of the semiconductor deviceincreases and the feature size of the semiconductor device shrinks, inthe semiconductor device manufacturing process, a plasma processingapparatus is used more and more often in order to perform various typesof processes such as film deposition, etching, and ashing. When such aplasma process is employed, a general advantage is obtained in thathighly accurate process control can be performed in an electronic devicemanufacturing process.

Conventionally, as a plasma processing apparatus to generate a plasmanecessary for the various types of processes described above, a CCP(Capacitively Coupled Plasma) processing apparatus and ICP (InductivelyCoupled Plasma) processing apparatus have been used (see patentreferences 1 and 2).

Of the two types of apparatuses, in the CCP processing apparatus,usually, a process chamber is usually employed which incorporates, as anupper electrode that forms one parallel plate, an Si top plate having ashower head structure to provide a more uniformed process gas flow, anda susceptor which can apply a bias to a lower electrode serving as theother parallel plate. In the plasma processing in this case, a substrate(target object) to be processed is placed on the susceptor. A plasma isgenerated between the upper and lower electrodes described above. Thesubstrate is subjected to a desired process with the generated plasma.

In the CCP processing apparatus, however, the plasma density is low whencompared to those of other plasma sources, and a sufficient ion flux isdifficult to obtain. Accordingly, the processing rate for the targetobject (wafer or the like) tends to be low. Even when the frequency ofthe power supply for the parallel plates is increased, a potentialdistribution appears within an electrode surface that constitutes eachparallel plate, so that the uniformity of the plasma and/or processtends to decrease. In addition, in the CCP processing apparatus, the Sielectrode consumes fast, and accordingly the COC (Cost of Consumable)tends to increase.

In the ICP processing apparatus, usually, a turn coil to which a highfrequency is to be supplied is arranged on a dielectric top plate (i.e.,outside a process chamber) which is located on the upper side of theprocess chamber. The arranged coil causes induction heating to generatea plasma immediately under the top plate. The target object is processedwith the generated plasma.

In the conventional ICP processing apparatus, a high frequency issupplied to the turn coil outside the process chamber (through thedielectric top plate) to generate a plasma in the process chamber. Whenthe diameter of the substrate (target object) increases, the processchamber needs a mechanical strength for the purpose of vacuum sealing.The thickness of the dielectric top plate must accordingly be increased,thus increasing the cost. In addition, when the thickness of thedielectric top plate increases, the power transmission efficiency fromthe turn coil to the plasma decreases. Therefore, the voltage of thecoil must be set high.

As a result, the dielectric top plate itself tends to be sputtered todegrade the COC described above. Furthermore, fine particles generatedby sputtering are deposited on the substrate to likely degrade theprocess performance. The size of the turn coil itself must also beincreased. To supply power to such a large-size coil, a high-outputpower supply is required.

In the conventional plasma process, power is supplied to a plasmachamber to which a gas is supplied, so as to plasmatize the gas, thusprocessing the base material set in the plasma chamber. The plasmaprocess has been designed such that uniform power is suppliedparticularly to the electrode to generate a spatially uniform plasma.The plasma uniformity, however, is largely influenced by the electrodeshape, the structure or the like of the plasma chamber, and parameterssuch as the pressure and gas species. Therefore, it is difficult toobtain an even plasma distribution that matches various processconditions.

Also, it is impossible to freely change the plasma generation area orthe like. For example, assume that a base material having an areasubstantially equal to that of the plasma generation space and a basematerial having an area much smaller than that of the plasma generationspace are to be processed. In this case, the plasma generation spacemust match the area of the larger base material. When coping with thebase material having the smaller area, even though most of the plasmageneration area is not used, the process is generally performed using alarge-area plasma.

A particle beam processing apparatus is available in which various typesof particles are selectively guided from a plasma source to a processchamber to process a base material in the process chamber. In thisapparatus, however, the density of the plasma source cannot besufficiently increased under a desired pressure, and the density of theparticles to be radiated cannot be increased sufficiently. It is alsodifficult to spatially control the particles so as to selectivelyirradiate a desired portion of the base material.

Another plasma processing apparatus is available in which, in order toincrease the plasma generation efficiency, a plasma chamber to which agas is supplied is connected to a plasma particle generation powersupply to plasmatize the gas under the atmospheric pressure, so as toprocess a base material in the chamber with the plasma. Thisatmospheric-pressure plasma processing apparatus is advantageous in thata plasma having a higher density can be obtained more easily than with aconventional reduced-pressure plasma processing apparatus.

In the atmospheric-pressure plasma processing apparatus, however, as thepressure is high, the dynamic range of the particleacceleration/deceleration energy is narrow.

The present applicant could not find any precedent technical reference,before the application, related to the present invention other thanthose specified by precedent technical reference information describedin this specification.

Patent Reference 1:

Japanese Patent Laid-Open No. 6-163467

Patent Reference 2:

Japanese Patent Laid-Open No. 7-058087

DISCLOSURE OF INVENTION

Problem to be Solved by the Invention

As described above, according to the prior art, a plasma source orplasma processing apparatus that can generate a high-density plasmahighly efficiently is not realized.

It is an object of the present invention to provide a plasma source orplasma processing apparatus in which the drawbacks of the prior artsdescribed above are solved.

It is another object of the present invention to provide a plasma sourceor plasma processing apparatus which can generate a high-density plasmahighly efficiently.

It is still another object of the present invention to provide a plasmasource or plasma processing apparatus which can radiate high-densityparticles.

It is still another object of the present invention to provide a plasmasource or plasma processing apparatus which can be controlled in timeand space.

Means of Solution to the Problem

The present inventors conducted extensive studies and found that toperform plasma discharge in holes of a hollow cathode electrode memberthrough which a gas could flow was very effective in achieving the aboveobjects.

A plasma source according to the present invention is base on the abovefindings and, more particularly, is a plasma source comprising at leasta chamber to which a gas should be supplied, and a hollow cathodeelectrode member which is arranged on a gas flow-out side of the chamberand has a plurality of electrode holes through which the gas can flow,characterized in that microcathode plasma discharge can be performed inthe electrode holes many marks of the hollow cathode electrode member.Four-dimensional (space+time) control is performed to generate a plasma.

According to the present invention, there is also provided a plasmaprocessing apparatus comprising at least a process chamber, basematerial holding means for arranging a base material at a predeterminedposition in the process chamber, and a plasma source to selectivelyirradiate the base material with a plasma (or a charged particle orradical selectively); characterized in that the plasma source includesat least a chamber to which a gas should be supplied, and a hollowcathode electrode member which is arranged on a gas flow-out side of thechamber and has a plurality of electrode holes through which the gas canflow, and microcathode plasma discharge can be performed in theelectrode holes of the hollow cathode electrode member.

According to a preferred aspect of the present invention, the electrodedescribed above comprises a multistage (two or more stages) electrodeelement.

According to another preferred aspect of the present invention, a plasmasource or plasma processing apparatus which is controllablefour-dimensionally (three spatial dimensions+time) is provided.

Effect of the Invention

As described above, according to the present invention, there isprovided a plasma source or plasma processing apparatus which cangenerate a high-density plasma highly efficiently.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic sectional view showing an embodiment of a plasmaprocessing apparatus which is configured to incorporate a plasma sourceaccording to the present invention.

FIG. 2 is a plan view showing the arrangement of a hollow cathodeelectrode member 4.

FIG. 3 is a sectional view sowing the arrangement of the hollow cathodeelectrode member 4.

FIG. 4 is a sectional view showing the arrangement of a hollow cathodeelectrode member according to another embodiment.

FIG. 5 is a sectional view showing the arrangement of a conventionalplasma processing apparatus configured to incorporate a conventionalplasma source.

FIG. 6 is a sectional view showing the arrangement of a hollow cathodeelectrode member according to another embodiment.

FIG. 7 is a sectional view showing the arrangement of a hollow cathodeelectrode member according to still another embodiment.

FIG. 8 is a schematic sectional view showing another arrangement exampleof the plasma source according to the present invention.

FIG. 9 is a schematic sectional view showing still another arrangementexample of the plasma source according to the present invention.

FIG. 10 is a schematic sectional view showing still another arrangementexample of the plasma source according to the present invention.

FIG. 11 is a perspective view schematically showing part of the plasmasource according to the present invention.

FIG. 12 is a plan view schematically showing part of the plasma sourceaccording to the present invention.

FIG. 13 is a sectional view schematically showing a generation exampleof high-speed neutral radicals according to the present invention.

FIG. 14 is a sectional view schematically showing a generation exampleof high-speed neutral radicals according to the present invention.

FIG. 15 is a sectional view showing an arrangement example of the plasmasource according to the present invention.

FIG. 16 is a sectional view showing an arrangement example of the plasmasource according to the present invention.

FIG. 17 is a sectional view showing an arrangement example of the plasmasource according to the present invention.

FIG. 18 is a sectional view showing an arrangement example of the plasmasource according to the present invention.

FIG. 19 is a sectional view showing an arrangement example of the plasmasource according to the present invention.

FIG. 10 is a sectional view showing an arrangement example of anelectrode that can be suitably used in a plasma source according to thepresent invention.

FIG. 21 is a correlation graph showing a relationship between the numberof vertical electrode pairs and the Kr emission intensity.

FIG. 22 is a schematic sectional view showing an example of thecombination of a plasma source according to the present invention andparallel-plate plasma electrodes.

FIG. 23 is a schematic sectional view showing a plasma processingapparatus used in an example.

FIG. 24 is a sectional view schematically showing an arrangement exampleof a coating apparatus which uses a plasma source according to thepresent invention.

FIG. 25 is a sectional view showing the arrangement of a conventionalcoating apparatus.

FIG. 26 is a sectional view schematically showing an arrangement exampleof another coating apparatus which uses a plasma source according to thepresent invention.

FIG. 27 is a sectional view showing part of the arrangement of a plasmasource according to the present invention.

FIG. 28 is a sectional view schematically showing an arrangement exampleof another coating apparatus which uses a plasma source according to thepresent invention.

FIG. 29 is a sectional view schematically showing an arrangement exampleof still another coating apparatus which uses a plasma source accordingto the present invention.

FIG. 30 is a sectional view schematically showing an arrangement exampleof a CNT forming device which uses a plasma source according to thepresent invention.

FIG. 31 is a perspective view showing part of the arrangement of thedevice shown in FIG. 30.

FIG. 32 is a plan view showing part of the arrangement of the deviceshown in FIG. 30.

FIG. 33 is a schematic sectional view showing another example of thecombination of a plasma source according to the present invention andparallel-plate plasma electrodes.

BEST MODE FOR CARRYING OUT THE INVENTION

The embodiments of the present invention will be described withreference to the drawings when necessary. In the following description,note that “part” and “%” which indicate an amount and ratio are based onthe mass standard, unless otherwise specified.

(One Embodiment of Plasma Source)

One embodiment of a plasma source according to the present inventionwill be described with reference to the schematic sectional view of FIG.1, the schematic plan view of FIG. 2, and the partial schematicsectional views of FIGS. 3 and 4. For the sake of comparison, FIG. 5shows a schematic sectional view of a conventional plasma source (whichplasmatizes a gas in a plasma preliminary chamber).

FIG. 1 is a schematic sectional view showing an embodiment of a plasmaprocessing apparatus which is configured to incorporate a plasma sourceaccording to the present invention. A plasma source 1 shown in FIG. 1incorporates a chamber 2 to which a gas should be supplied and a hollowcathode electrode member 4 which is arranged on the gas flow-out side ofthe chamber 2 and has a plurality of electrode holes 3 through which thegas can flow. Referring to FIGS. 2 and 3, the hollow cathode electrodemember 4 comprises pairs of porous conductor members 4 b which arecombined through dielectric porous spacers 4 a.

As shown in FIG. 1, a DC power supply 6 is connected to be able to applya voltage between each pair of porous conductor members 4 b. A DC powersupply 7 is also connected to be able to apply a voltage between eachporous conductor member 4 b and the chamber 2. Thus, the voltage isapplied between each pair of porous conductor members 4 b, while flowinga gas through the electrode holes 3, to start DC-driven microcathodedischarge, thereby generating a plasma in regions P shown in FIG. 3.

The plurality of pairs of porous conductor members 4 b are set in thevertical direction, and a voltage is externally applied to therespective pairs independently of each other. When the plasma isgenerated, electrons collide against the inner walls of the electrodeholes 3 to emit electrons (secondary electrons) from the inner walls ofthe electrode holes 3 by a γ (gamma) function. According to the presentinvention, the electrons are emitted from the inner walls of theelectrode holes 3 by the γ function, and the emitted electrons collideagainst next molecules to ionize the molecules. This α (alpha) functionmaintains discharge.

Alternatively, an electrode may be arranged to be electrically separatedfrom the chamber 2, and a DC or AC electric field may be applied betweenthe arranged electrode and the chamber 2 to generate a plasma in thechamber 2. Microwaves may also be used. To enhance the γ function, asthe metal that forms the electrode portion, a member which has a highplasma resistance and efficiently generates secondary electrons is used.Alternatively, the electrode portion can be coated with carbonnanotubes.

When necessary, the surface of the electrode portion may be coated witha metal material or the like having a small work function, e.g., Cs orOs that has a high efficiency of electron emission from the surface, asneeded. Also, a structure may be possible in which the surface of theelectrode metal is coated with an insulator to decrease the apparentwork function. In the case of DC discharge, such coating can beappropriately adjusted or removed.

As shown in the partial schematic sectional view of FIG. 4, the hollowcathode electrode member 4 described above may have the plurality ofpairs of porous conductor members 4 b, when necessary, which arecombined through the porous spacers 4 a. This embodiment having theplurality of pairs of porous conductor members 4 b in this manner cancontrol the energy of the charged particles and prevent a decrease inthe energy of the charged particles while passing through the holes. Theelectrode holes 3 are extracting electrodes. When a voltage is appliedto the extracting electrodes appropriately, plasma charged particles(positive/negative ions) and radicals can be extracted. The plurality ofelectrode holes 3 may be distributed so that the plasma, chargedparticles, and radicals extracted from the electrode holes 3 distributesubstantially uniformly on an electronic machinery.

(Plasma Processing Apparatus)

The plasma processing apparatus according to the present inventionincorporates at least a process chamber 10, a base material holdingmeans 11 for arranging a base material 12 for an electronic device orthe like at a predetermined position in the process chamber 10, and theplasma source having the arrangement described above to irradiate thebase material 12 for the electronic device or the like with a plasma (orcharged particles or radicals selectively).

In the embodiment of the plasma processing apparatus shown in FIG. 1,the target object (e.g., a wafer) 12 on the susceptor (base materialholding means) 11 which is arranged in the process chamber 10 loadedwith the plasma source 1 according to the present invention can beprocessed with the plasma by plasma generation based on microcathodedischarge in the electrode holes 3. A bias power supply 13 is connectedto the susceptor 11 to be able to apply a predetermined voltage (e.g.,an RF voltage) to the susceptor 11.

An electrode may be arranged to be electrically separated from a lowerchamber space 14, and a DC or AC electric field may be applied betweenthe arranged electrode and the chamber to generate a plasma in thechamber 14. Microwaves may also be used. At this time, electrons,radicals, and ions can be injected from a plasma generated bymicrocathode discharge into the plasma generated in the chamber 14. Thebase material 12 can be processed with the plasma containing theinjected particles.

The plasma source having the arrangement described above according tothe present invention can generate a plasma based on good microcathodedischarge relatively without being influenced by a gas pressure underwhich the plasma source is driven. In other words, the plasma sourceaccording to the present invention can easily realize anatmospheric-pressure plasma (with a pressure of about 101.3 kPa;densities of the electrons, ions, and radicals are generally about10¹⁵/cm³) having a prodigiously higher density than that of a so-calledlow-pressure plasma (with a pressure of about 0.133 Pa to 13.3 Pa;densities of electrons, ions, and radicals are generally about 10¹¹ to10¹²/cm³). When such an atmospheric-pressure plasma is used, stabledischarge can be performed under the atmospheric pressure, so that aso-called non-equilibrium plasma having an electron temperature higherthan the gas temperature can be suitably realized.

In contrast to this, in the conventional plasma source or plasmaprocessing apparatus as shown in FIG. 5, it is generally difficult todecrease the conductance and increase the pressure in the plasmapreliminary chamber. As the pressure in the preliminary chamber is a lowgas pressure, a high-density plasma is difficult to obtain (the plasmageneration space is large and accordingly the apparatus becomes bulky),and while the charged particles or radicals pass through the holes,their density tends to decrease. Also, the dynamic range of the particleacceleration/deceleration energy is small. As particleacceleration/deceleration is applied to the electrode uniformly,spatially independent control is impossible to perform.

(Arrangement of Respective Portions)

The respective portions and the like that constitute the plasma sourceor plasma processing apparatus according to the present invention willbe described in detail.

(Chamber)

Regarding the chamber 2 shown in FIG. 1 to which the gas is to besupplied, as far as a gas for plasma generation can be supplied into thechamber 2 and the plasma source can be arranged on the gas flow-outside, the structure, size, material, and the like of the chamber 2 arenot particularly limited. An electrode may be arranged to beelectrically insulated from the chamber 2 so as to generate a plasma inthe chamber 2.

(Hollow Cathode Electrode)

The hollow cathode electrode 4 has the plurality of electrode holes 3.As far as plasma generation in the electrode holes 3 is possible, thenumber and size of the electrode holes 3, the thickness of the hollowcathode electrode member 4, and the like are not particularly limited.To obtain low conductance, preferably, the sum (S) of the hole areas andthe hole length (L) establish a certain relationship. S≦α·L. Accordingto the present invention, a relationship (metal thickness)>(insulatorthickness) is preferably satisfied in the microcathode. This is becausethe area of the electrode hollow cathode increases and accordinglyelectrons are readily generated from the surface of the hollow cathodeelectrode, which is advantageous in terms of an increase andstabilization of discharge volume.

(Porous Spacer Member)

As described above, the hollow cathode electrode 4 includes at least oneset of a pair of porous conductor members combined through a dielectricporous spacer member. As far as plasma generation in the electrode holes3 is possible, the material, size, thickness, and the like of the porousspacer member 4 a are not particularly limited. In terms of preventionof leakage between the electrodes or abnormal discharge, the porousspacer member 4 a preferably has the following arrangement.

Material of porous spacer member 4 a:

SiO₂, Al₂O₃, AlN, BN, BNC, or the like

Size: Dielectric hole diameter≧Electrode hole diameter

Thickness: Sufficient to prevent leakage and dielectric breakdown and toobtain an appropriate discharge space.

According to the present invention, the electrode may be made of SUS andcarbon nanotubes may be grown on the electrode made of SUS.Alternatively, the electrode may be coated with Cs, Os, or the likehaving high electron emissivity.

(Porous Conductor Member)

As far as plasma generation in the electrode holes 3 is possible, thematerial, size, thickness, and the like of the porous conductor members4 b are not particularly limited.

The material of the porous conductor members 4 b is preferably Si, SUS,Mo, W, or the like. The thickness of each member 4 b is preferably 1 μmor more.

(Gas)

The gas that can be used in the present invention and should be suppliedinto the chamber 2 is not particularly limited, and various types ofgases can be used in accordance with the objects of the plasma process.More specifically, when the plasma process is etching, an etching gascan be used. When the plasma process is film deposition, a filmdeposition gas can be used. In addition, various types of inert gases(e.g., a rare gas) can be used as a plasma generation gas. Gases thatcan be suitably used in the present invention are as follows.

Plasma generation gas: Ar, He, H₂, N₂, Xe, Kr, Ne

Etching gas: CF₄, C₄F₈, C₄F₆, NF₃, H₂O, SF₆, Cl₂, O₂, Br₂, NH₃

Film deposition gas: SiH₄, CH₄, C₂H₂, organic gas

Of the above gases, as the plasma generation gas, Kr or Xe is preferablyused in terms of plasma stability because it decreases a dischargemaintaining voltage.

(Plasma Generation Principle)

According to the present invention, as far as plasma generation in theelectrode holes 3 is possible, the plasma generation principle is notparticularly limited. More specifically, while a DC voltage is appliedbetween the pair of porous conductor members 4 b in the embodiment ofFIG. 1 described above, the DC voltage can be replaced by microwaves oralternating current (high-frequency RF, VHF, or UHF).

In the embodiment wherein the DC voltage is applied, the followingcondition can be suitably employed.

Voltage: 1 kV or more

In the embodiment wherein microwaves (e.g., 2.45 GHz) are applied, thefollowing condition can be suitably employed.

Microwaves: preferably 0.5 W/cm². The microwaves may be adjusted whennecessary in accordance with the electrode area

(Base Material for Electronic Device or the Like)

When the plasma source or plasma processing apparatus according to thepresent invention is employed, the base material (e.g., base materialsfor various types of electronic devices or the like; e.g., a wafer) canbe processed with a plasma. Application to processes such as etching,deposition, a surface process, or the like using plasma chargedparticles or radicals is possible. The base material for the electronicdevice or the like described above that can be used in the presentinvention is not particularly limited, and one type or a combination oftwo or more types of known base materials for electronic devices or thelike can be selectively used. An example of such a base material for anelectronic device or the like includes a semiconductor material, liquidcrystal device material, organic material, and the like. An example ofthe semiconductor material includes a material containing single-crystalsilicon as a major component, poly-crystal Si, an SiO₂ oxide, and thelike.

Other Embodiments

The partially sectional schematic views of FIGS. 6 and 7 show a hollowcathode electrode 4 according to other embodiments. In the embodimentshown in FIG. 6, a hollow cathode electrode 4 comprising a pair ofporous conductor members 4 b combined through a porous spacer member 4 ais attached to a grounded metal member 21 through a dielectric 20.Except for this, the arrangement of the embodiment shown in FIG. 6 isthe same as that shown in FIG. 1. In the arrangement shown in FIG. 6,the porous spacer member 4 a is made of a dielectric such as alumina(Al₂O₃) or quartz, and the porous conductor members 4 b are made of ametal such as Si, Cu, Mo. W, or SUS.

Referring to FIG. 7, a hollow cathode electrode 4 comprising a pluralityof pairs of porous conductor members 4 b combined through porous spacers4 a is attached to a grounded metal member 21 through a dielectric 20,and an extracting electrode 22 is arranged under the hollow cathodeelectrode 4. Except for this, the arrangement of FIG. 7 is the same asthat of the embodiment shown in FIG. 1.

The extracting electrode 22 is grounded through a variable-voltage powersupply 23. A voltage V is applied to the extracting electrode 22. Whenthe voltage V=0 or a floating potential, radicals or a plasma isextracted from the extracting electrode 22. When the voltage V>0,electrons or negatively charged ions are extracted from the extractingelectrode 22. When the voltage V<0, positively charged ions areextracted from the extracting electrode 22. When extracting the plasma,the extracting electrode 22 can be omitted. In the process of extractingpositive/negative ions, the positive/negative ions may be collidedagainst the side wall to neutralize the ions, so that radicals having anenergy are extracted.

In the embodiment of FIG. 7, a distance d between the extractingelectrode 22 and the porous conductor member 4 b which is the closest tothe extracting electrode 22 is preferably about 1 mm to 10 mm, althoughit depends on the operating condition of the hollow cathode electrode 4and/or extracting electrode 22.

According to the present invention, the particle density can be greatlyincreased to stabilize discharge. From the viewpoint of controlling theparticles four-dimensionally (time and space) to enable radiation, themicrocathode is preferably a “multistage” (preferably three sages ormore) microcathode. From the viewpoint of increasing the plasmacharacteristics, a multistage microcathode having three or moreelectrodes is preferable. When a single-stage microcathode is employed,a “pressure difference” is preferably provided between the gas supplyside and plasma generation side from the viewpoint of increasing theprocess dynamics.

In the plasma source of the present invention, the high pressure sidecan be at the atmospheric pressure. The plasma generation side can be atthe atmospheric pressure, or a pressure lower than the atmosphericpressure. In terms of plasma generation efficiency, preferably, thepressure at any one (and furthermore two) of the gas supply side andplasma generation side is high.

The microcathode source according to the present invention can be usedalone as a plasma source, and can be combined with a conventional plasmagenerating means (e.g., parallel plates) when necessary. When themicrocathode source is combined with the conventional plasma generatingmeans in this manner, various types of particles can be injected into aconventional plasma process. This provides an advantage that the processperformance can be greatly improved under the conventional processconditions.

Furthermore, a large number of microcathodes may be planarly provided.Using the holes of the plurality of microcathodes as “addresses”,control operation using a computer or the like may be performed, toadjust turn on/off of the respective holes, or the plasma intensityand/or its planar distribution.

A plasma having a shape that matches the shape of a substrate to beplasma-processed can be generated by the planar control of the plasmaintensity described above. Planar control of the plasma intensityenables selective etching (e.g., etching that does not use a resist) ofthe substrate.

In the electrodes of a multistage microcathode, potentials to be appliedto the respective electrodes may be differed to adjust the plasmaintensity in the vertical direction. In this case, when the potentialsto be applied to the respective electrodes are made different, thegenerated plasma can be controlled to be neutron-rich. For example, witha vertical multistage electrode, when a plasma is generated only in theupper portion, the plasma intensity and particle density can becontrolled highly accurately.

According to the present invention, CNTs (Carbon NanoTubes) can begenerated on the respective electrodes that constitute the plasmasource, so that the γ electron efficiency of the plasma source may beincreased (regarding the details of the CNT forming method, the CNTs canbe formed in accordance with thermal CVD or plasma CVD by increasing thetemperature of the electrode materials).

An example of another arrangement of the plasma source according to thepresent invention is shown in the schematic sectional view of FIG. 8 (anexample in which the plasma source has a four-stage arrangement) andthat of FIG. 9 (an example in which the plasma source has a three-stagearrangement).

As shown in FIG. 10, the apparatus according to the present inventioncan form a “three-dimensional multiarray plasma source” or“three-dimensional multiarray particle supply apparatus” in which aplurality of multiarrays are formed on a two-dimensional plane and aplurality of vertical electrodes are arrayed in the vertical directionin one array.

Voltages can be applied to the respective pairs of electrodes of thethree-dimensional multiarray electrodes independently of each other. Inthe chamber shown in FIG. 1, a sample 12 having a three-dimensionalshape is set on the susceptor. A sample having a two- orthree-dimensional shape can be processed by a high-speed radical processin which the plasma, charged particles, radicals, and energy arecontrolled, in accordance with the sample shape (not onlytwo-dimensionally but also three-dimensionally), as shown in, e.g.,FIGS. 11 and 12, by controlling the power supply appropriately by FDD.

Conventionally, a plasma which is larger than at least the shape of thetarget object is required. Meanwhile, with the apparatus of the presentinvention, the shape of the plasma can be flexibly changed in accordancewith the dimension and size of the target object. In the case of anordinary plasma process, a shima (sheath) is formed between the plasmaand a target object. Three-dimensionally, ions are radiated through theformed shima (sheath). The ion energy cannot be changed in accordancewith the shape.

With the apparatus of the present invention, for example, the voltage ofthe extracting electrode shown in FIG. 13, or the voltage between theanode electrode and cathode electrode of a pair of verticalmultielectrodes shown in FIG. 14 is controlled, so that radiation ofenergy-controlled high-speed positive/negative ions or high-speedradicals becomes possible three-dimensionally. Therefore,three-dimensional solid structure having a desired shape can be directlyprocessed or deposited without using a mask pattern or the like.

For example, the respective plasma sources can be on/off-modulatedindependently on the order of several psec to msec. These processes canbe controlled on the time axis, so that a four-dimensional plasmaprocess using four-dimensional multiarray electrodes can be performed.

FIGS. 15, 16, 17, 18, and 19 show arrangement examples of a microplasmasource that can be used in the present invention.

(Gas Deposition)

According to the experiment conducted by the present inventor, when Kror Xe gas is introduced, the plasma tends to stabilize. From thisviewpoint, He gas is preferable to Ar gas, and Kr or Xe gas ispreferable to He gas.

(Electrode Structure)

As shown in FIG. 20, when the insulator is recessed by 0.1 mm from theconductor electrode, discharge tends to stabilize.

(Kr Emission Intensity)

FIG. 21 shows a measurement result of the Kr emission intensity measuredby the present inventor.

Plasma diameter: 0.1 mm; Metal Cu: 1 mm;

Insulator Al₂O₃: 0.2 mm

Conditions of this experiment:

The Kr gas was flown from the upper portion. A voltage of 175 V wasapplied at 3.35 mA to the first and second electrode pairs under theatmospheric pressure. As shown in FIG. 21, a plasma was generated by thecathode (A) and cathode (B). The Kr emission intensity (877.7 nm and760.2 nm) when the plasma was generated was observed by a photodiode toobtain 41 nW. Subsequently, a voltage of 350 V was applied to thecathode electrode (C) of the third electrode pair at 1.45 mA to obtain aphotodiode output of 61 nW. In this manner, it was observed that anoutput from the multistage electrodes increased proportionally to theumber of plasmas.

EXAMPLE 1

An example will be described in which the apparatus of the presentinvention is applied to pressurization of a gate electrode for thefabrication of a MOS transistor.

A poly-silicon film (thickness: 500 nm) formed on an underlying siliconoxide film (50 nm) is etched using a resist film (100 nm) as a mask. Asthe multielectrodes, 25 porous electrodes are fabricated each having adiameter of 100 μm and comprising a pair of a metal electrode andinsulator.

He/Cl₂ gas or Xe/Cl₂ is introduced under the atmospheric pressure fromthe upper portion and is evacuated through the porous electrodes tomaintain a reaction point pressure at 1 Torr. The sample described aboveis set 2.5 mm below the electrodes and is etched.

As the multielectrodes, five pairs of electrodes are set with respect tothe lower extracting electrode, and a voltage was applied to theelectrodes. A plasma is generated in the vicinity of the five pairs ofcathode electrodes. As the ion species in the plasma, He⁺, or Xe⁺, Cl⁺,and Cl₂ ⁺ are present. The ions are accelerated toward the lowerextracting electrode and neutralized by the lower electrode. The lowerelectrode radiates high-speed He, or Xe, Cl, and Cl₂ particles towardthe sample.

The speed of the high-speed particles depends on the voltage applied tothe electrode and the structure of the lower electrode, and can becontrolled within the range of about 5 eV to 15 eV.

When etching was performed by radiating the neutral radicals, an etchingselectivity of 100 or more with respect to the SiO₂ resist was obtainedat an etching rate of about 500 nm/min. Damage-free processing free fromcharge-up by charged particles can be performed. When the experimentalconditions are optimized appropriately, microprocessing of poly-siliconwith a vertical width of about 10 nm can be performed.

When the distance between the plasma generation and lower electrode isincreased, the pressure is increased, or the plasma is pulse-changed, alarge amount of Cl— ions may be generated, and the sample may beirradiated with Cl— from the extracting electrode. Alternatively, theextracting electrode may be irradiated with Cl— to generate Cl neutralradicals.

EXAMPLE 2

The arrangement of this apparatus is basically the same as that ofExample 1. As the gas (A), H₂/Xe gas is introduced under the atmosphericpressure from above the multielectrodes.

Evacuation is performed through the multielectrodes to maintain thepressure in the lower reaction chamber at about 10 Torr. SiH₄/H₂ orSiH₄/Xe gas is introduced from the lower electrode to deposit acrystallite silicon thin film on the glass substrate. The substratetemperature is set to 300° C. The glass substrate is used as the samplethe distance between the multielectrodes and the sample is about 10 mm.

In the multielectrodes, a large amount of H radicals are generated bythe reaction of H₂+e→H+H, Xe+e→Xe⁺+e+e and introduced into the reactionchamber. The substrate is irradiated with high-speed H radicals with anenergy of about 5 eV or less in the same manner as in Example 1.

A large amount of SiH₃ radicals are generated by the reaction of H+SiH₄→SiH₃+H₂ to serve as a thin-film precursor.

The interaction of the high-speed H radicals and SiH₃ radicals forms ahigh-quality micro-crystallite silicon thin film on the glass substrate.With this method, both the R radical density and the SiH₃ density becomehigh, and the two types of radicals can be controlled independently ofeach other. Consequently, a defect-free micro-crystallite silicon oramorphous silicon film can be formed.

Furthermore, as shown in FIG. 22, when high-frequency power of 100 MHzis applied between the lowermost electrode of the multielectrodes andthe substrate electrode 2, a capacitively coupled SiH₄/H₂ plasma excitedat 100 MHz can be applied, and high-density H radicals can be insertedin the plasma. When UHF-band high-frequency power of 400 MHz to 500 MHzis used at this time, the same result can be obtained. The distancebetween the lowermost electrode and the substrate electrode must bechangeable in accordance with the operation pressure. A pressure ofabout 10 Torr (about 1 Torr to 20 Torr) is desirable, but a pressure of1 Torr to 300 Torr will do.

EXAMPLE 3

The arrangement of this apparatus is basically the same as that ofExample 2. High-frequency power of 400 MHz and that of 450 KHz areapplied to the substrate electrode 2 (FIG. 23). As the gas (A), a gassuch as Ar, O₂, or N₂ is introduced from the above the multielectrodesat the atmospheric pressure. C₄F₆, C₄F₈, or the like is introduced fromthe lower electrode to form on the Si substrate. SiO₂, SiOCH, organicfilm SIC, SiCN, or the like is processed using a patterned resist or thelike as a mask.

Ar⁺, O⁺, or N⁺ electrons, or O or N radicals are generated in themultielectrodes to inject various types of energy-controlled particlesinto the reaction chamber.

In the reaction chamber, a plasma has been generated by the 400-MHzhigh-frequency with the gas such as C₄F₈ or C₄F₆. Ions in the plasma areintroduced into the substrate by the 450-KHz high frequency. Whether the450-KHz high frequency is to be applied or not may be decidedappropriately in accordance with the process.

The plasma of the gas such C₄F₈ or C₄F₆ mainly generates CF₂ radicals.

When high-speed (high-energy) electrons are injected into the plasmathrough the multielectrodes, the electrons in the plasma form a doubledistribution comprising a low energy and high energy.

The injected high-speed electrons can promote ionization to greatlyincrease the CF₃ ⁺ density in the plasma. At this time, CF₂ radicals areformed of C₄F₈ and C₄F₆ mainly by low-energy electrons.

Accordingly, the film such as an SiO₂ or SiOCH film can be processedhighly accurately using the CF₂ radicals and CF₃ ⁺ ions as major activespecies. Alternatively, O₂ or N₂ may be introduced to inject O⁺, N⁺, andO, and high-speed O and N radicals into the C₄F₈ or C₄F₆ plasma so as toprocess the SiO₂ or SiOCH organic film. When the conditions areappropriately selected as well as the material process, high-rateetching can be realized with a vertical shape. While 400 MHz is used inthis research, the frequency can be appropriately selected in the rangeof about 60 MHz to 500 MHz.

In the semiconductor device, conventionally, the design rule is finelydetermined to promote a high integration density and/or highperformance. When the design rule becomes very fine (e.g., about 0.18 μmor less), an increase in wiring resistance and in wiring-to-wiringcapacitance becomes conspicuous. With the conventional wiring material,to improve the performance of the device any further is difficult.

For example, to increase the operation speed of the semiconductordevice, the speed of the electrical signal must be increased. With theconventional aluminum wiring, however, if the feature size of thesemiconductor device shrinks more (for example, to about 0.18 μm orless), a limit is posed to the speed of the electrical signal flowingthrough a circuit that forms the semiconductor device (a so-called“wiring delay” occurs). Therefore, a wire made of a material, e.g.,copper (Cu), which has lower electrical resistance than that of aluminummust be used. As Cu has lower electrical resistance than aluminum, thewiring delay decreases, and electricity flows smoothly even when thewiring is thin.

When a material such as copper having low electrical resistance asdescribed above is to be used, as an insulating film, an “insulatingfilm from which” electricity is less likely to “leak” must be used. Thisis because when such a Cu wiring through which electricity flows easilyand an insulating film from which electricity will not leak easily arecombined, a semiconductor device that operates at a very high speed canbe fabricated.

In the times when a conventional aluminum wiring was used, an SiO₂ film(relative dielectric constant=4.1) was used as an insulating film. Whena Cu wiring is to be used, an insulating film having a relativedielectric constant (Low-k) much lower than that of the SiO₂ film isnecessary. In general, a Low-k film signifies a film having a relativedielectric constant of 3.0 or less.

To fabricate a Low-k film, two methods are conventionally known. Onemethod uses a CVD apparatus. With this method, although a high-qualityLow-k film can be obtained, the productivity of Low-k film fabricationis naturally low and accordingly the running cost is high. According tothe other method, a Low-k material such as a liquid having fluidizationis applied the base material or the like using a spin coater or the like(a method of forming a so-called SOD (Spin On Dielectric) insulatingfilm). With the coating method, an excellent running cost andproductivity can be obtained.

Regarding a coating film obtained by the spin coating method describedabove, in order to obtain desired characteristics, various types ofattempts have been conventionally made vigorously in which adjustment ofthe constituent components of the solution to be applied for coating,the molecular structure of the material, annealing after coating, andthe like are appropriately combined to control the chemical structure ofthe coating film to be obtained.

Depending on the conventional attempts described above, however, desiredgood characteristics (e.g., good durability which is required when theresist is to be ashed after etching) cannot always be obtained easily.For example, it is pointed out that a Low-k insulating film formed ofSOD has a low mechanical strength and, particularly, an organicinsulating film tends to lack in ashing resistance.

In contrast to this, with the apparatus according to the presentinvention, the drawbacks of the prior art described above are solved,and a coating film having high film quality can be formed as will bedescribed hereinafter.

Other embodiments of the present invention will be describedhereinafter. In the following description, the present invention will bedescribed in more detail with reference to the drawings when necessary.In the following description, note that “part” and “%” which indicate anamount and ratio are based on the mass standard, unless otherwisespecified.

(One Embodiment of Plasma Source)

One embodiment of a plasma source according to this mode will bedescribed with reference to the schematic sectional view of FIG. 24. Forthe sake of comparison, FIG. 25 shows a schematic sectional view of aconventional spin coating apparatus (which performs only spin coating ina process chamber).

FIG. 24 is a schematic sectional view showing one embodiment of acoating apparatus which is configured to incorporate a plasma sourceaccording to the present invention. The plasma source shown in FIG. 24incorporates a chamber 102 to which a gas is should be supplied and ahollow cathode electrode member 104 which is arranged on the gasflow-out side of the chamber 102 and has a plurality of electrode holes103 through which the gas can flow. The hollow cathode electrode member104 comprises pairs of porous conductor members 104 b which are combinedthrough dielectric porous spacers 104 a.

As shown in FIG. 24, a DC power supply (not shown) is connected to beable to apply a voltage between each pair of porous conductor members104 b. A DC power supply 107 is also connected to be able to apply avoltage between each porous conductor member 104 b and the chamber 102.Thus, the voltage is applied between each pair of porous conductormembers 4 b, while flowing a gas through the electrode holes 103, tostart DC-driven microcathode discharge, thereby generating a plasma. Theregion where the plasma is generated is similar to that described withreference to FIG. 3.

When the plasma is generated, electrons collide against the inner wallsof the electrode holes 103 to emit electrons (secondary electrons) fromthe inner walls of the electrode holes 103 by a γ (gamma) function. Inthe apparatus shown in FIG. 24, the electrons are emitted by the γfunction, and the emitted electrons collide against next molecules toionize the molecules. This a (alpha) function maintains discharge.

When necessary, the hollow cathode electrode member 104 described abovemay have the plurality of pairs of porous conductor members 104 bcombined through the porous spacers 104 a. This is the same as in thearrangement shown in FIG. 4. This embodiment of having the plurality ofpairs of porous conductor members 104 b is preferable because thepressure drop is increased and attenuation of the plasma density can beprevented. In this case, the plasma can be stably generated, which isanother advantage.

(Coating Apparatus)

The coating apparatus shown in FIG. 24 incorporates at least a processchamber 110, a rotatable base material holding means 11 for arranging anelectronic device base material 112 at a predetermined position in theprocess chamber 110, and a plasma source having the arrangementdescribed above to irradiate the electronic device base material 112with a plasma.

In the coating apparatus shown in FIG. 24, the target object (e.g., awafer) on the susceptor 111 which is arranged in the plasma processchamber 110 loaded with the plasma source can be processed by plasmageneration based on microcathode discharge in the electrode holes 103.The susceptor 111 is rotatable. A bias power supply (not shown) isconnected to the susceptor 111 to be able to apply a predeterminedvoltage (e.g., an RF voltage or DC voltage) to the susceptor 111. As thesusceptor 111 is rotated by this arrangement, a bias can be applied tothe susceptor 111. The temperature of the susceptor can be changed tocool or heat the substrate, thereby depositing a film.

A coating material supply means 120 can supply a predetermined coatingmaterial 121 onto a machinery 112. With this arrangement, the coatingmaterial is supplied onto the machinery 112, while irradiating themachinery 112 with a plasma, to form a coating layer on the machinery112.

The plasma source having the arrangement described above according tothe present invention can generate a plasma based on good microcathodedischarge relatively without being influenced by a gas pressure underwhich the plasma source is driven. In other words, the plasma sourceaccording to the present invention can easily realize anatmospheric-pressure plasma (with a pressure of about 101.3 kPa;densities of electrons, ions, and radicals are generally about 10¹⁵/cm³)having a prodigiously higher density than that of a so-calledlow-pressure plasma (with a pressure of about 0.133 Pa to 13.3 Pa;densities of electrons, ions, and radicals are generally about 1011 to10¹²/cm³).

When such an atmospheric-pressure plasma is used, stable discharge canbe performed under the atmospheric pressure, so that a so-callednon-equilibrium plasma having an electron temperature higher than thegas temperature can be suitably realized. In particular, when aplurality of plasmas are generated vertically, plasma stabilization canbe achieved.

In contrast to this, in the conventional plasma source or coatingapparatus as shown in FIG. 25, as the plasma is generated in the plasmapreliminary chamber (not shown), it is generally difficult to decreasethe conductance and increase the pressure in the plasma preliminarychamber. Also, the dynamic range of the particleacceleration/deceleration energy is small. When the voltage to beapplied to the plasma source is appropriately changed, the high-densityatmospheric-pressure plasma can radiate a plasma, electrons,positive/negative ions, and neutral radicals separately. Also,accelerated positive/negative ions may be neutralized by the wall of theplasma source or in the gas phase to radiate high-speed neutralradicals.

(Arrangement of Respective Portions)

The respective portions and the like that constitute the plasma sourceor coating apparatus according to the present invention will bedescribed in detail.

(Chamber)

Regarding the chamber 102 shown in FIG. 24 to which the gas is to besupplied, as far as a gas for plasma generation can be supplied into thechamber 102 and the plasma source can be arranged on the gas flow-outside, the structure, size, material, and the like of the chamber 102 arenot particularly limited.

(Hollow Cathode Electrode Member)

The hollow cathode electrode member 104 has the plurality of electrodeholes 103. As far as plasma generation in the electrode holes 103 ispossible, the number and size of the electrode holes 103, the thicknessof the hollow cathode electrode member 104, and the like are notparticularly limited.

(Porous Spacer Member)

As described above, the hollow cathode electrode 4 includes at least oneset of a pair of porous conductor members combined through a dielectricporous spacer member. As far as plasma generation in the electrode holes103 is possible, the material, size, thickness, and the like of theporous spacer 4 a are not particularly limited.

(Porous Conductor Member)

As far as plasma generation in the electrode holes 103 is possible, thematerial, size, thickness, and the like of the porous conductor members104 b are not particularly limited.

(Gas)

The gas that can be used in the present invention and should be suppliedinto the chamber 102 is not particularly limited, and various types ofgases can be used in accordance with the purposes of the plasma process.More specifically, usually, various types of inert gases (e.g., a raregas such as argon) can be used as a plasma generation gas.

(Plasma Generation Principle)

According to the present invention, as far as plasma generation in theelectrode holes 103 is possible, the plasma generation principle is notparticularly limited. More specifically, while a DC voltage is appliedbetween the pair of porous conductor members 104 b in the apparatusshown in FIG. 24, the DC voltage can be replaced by high-frequency wavesor microwaves.

Other Embodiments

FIGS. 26 and 27 show coating apparatuses according to other embodimentsof the present invention. In the embodiments shown in FIGS. 26 and 27,the uppermost portion of a hollow cathode electrode member 104 comprisesdielectric porous spacers 104 a so that discharge can readily focus onthe electrode holes 103.

(Electronic Device Base Material)

When the plasma source or coating apparatus described above is employed,various types of electronic device base materials (e.g., a wafer) can beprocessed with a plasma. The electronic device base material describedabove that can be used in the present invention is not particularlylimited, and one type or a combination of two or more types of knownelectronic device base materials can be selectively used. An example ofsuch a electronic device base material includes a semiconductormaterial, liquid crystal device material, and the like. An example ofthe semiconductor material includes a material containing single-crystalsilicon as a major component, SiC, GaAs, and the like.

In the present invention, other than those described above, any materialthat contains at least Si, C, and/or a metal or the like and that isliquid in the vicinity of a normal pressure can be used with anyparticular limitations.

In the present invention, for example, a coating material and thecoating process which can be used in the conventional sol-gel method canbe employed with any particular limitations.

In the present invention, a material (coating-difficult material) thatis difficult to use for coating in the conventional process, a high-kmaterial (e.g., a high-dielectric-constant thin film HfO), and aferroelectric thin film (e.g., BST, i.e., a thin film containing Bi, Si,and/or Ti) can be used for coating.

(Coating Method)

In the coating method which uses the apparatus shown in FIG. 24 or 26,while irradiating an electronic device base material arranged in theprocess chamber with a plasma, a coating material is supplied onto theelectronic device base material to form a coating layer on the basematerial. During forming the coating layer (in the coating process), thepressure of the plasma process may be changed. During supply of thecoating material, the pressure for the plasma process can be changedover time to change a film structure to be formed on the electronicdevice base material periodically and/or inclinedly so as to form acoating layer having a multilayer structure and/or inclined structure.

(On Electronic Device Base Material)

In the present invention, a state “on the electronic device basematerial” is sufficiently established as far as the coating film to beformed is located above the electronic device base material (that is,above that side of the base material where respective layers whichconstitute the electronic device are formed). In other words, anotherinsulating layer, conductor layer, semiconductor layer, or the like maybe arranged between the machinery and coating film. Naturally, aplurality of various types of insulating layers, conductor layers,semiconductor layers, or the like including the coating film to beformed in the present invention may be arranged when necessary.

(Coating Material)

The coating material that can be used in the present invention is notparticularly limited, and any organic material and/or inorganic materialcan be used. The material may be, e.g., a solution. As such an organicmaterial and/or inorganic material, for example, a curable material canbe used.

(Curable Material)

The curable material that can be used in the present invention is notparticularly limited. From the viewpoint of a suitable combination witha good-conductivity wiring material such as Cu, a curable material thatprovides an insulating film having a dielectric constant of 3 or lessafter cure is preferable.

As such a curable material, for example, a low-dielectric-constantorganic insulating film having a dielectric constant of 3 or less can beused, and an organic polymer such as PAE-2 (manufactured by Shumacher),HSG-R7 (manufactured by Hitachi Chemical Co., Ltd), FLARE (manufacturedby Aplied Signal), BCB (manufactured by Dow Chemical), SILK(manufactured by Dow Chemical), or Speed Film (manufactured by W. L.Gore) can be used.

(How to Arrange Curable Material)

How to arrange the curable material on the electronic device basematerial is not particularly limited. From the viewpoint ofsimplification of the apparatus, a solution or dispersion of a fluidcurable material is preferably applied to the electronic device basematerial. This coating is preferably spin coating.

(Example of Suitable Condition)

In the present invention, for example, the following conditions can besuitably used.

Microwaves: 2 kW/cm²; a DC voltage may be supplied to the hollow cathodeplasma source. 1 to 10 W/cm²

Gas: Ar, 1,000 sccm+N₂, 100 sccm, or Kr, 1,000 sccm+N₂, 100 sccm, or H₂or CO₂

He: Appropriately

O₂:

Pressure: 1 to 760 mTorr (133 to 10×10⁴ Pa)

Base material temperature: 350±50° C.

Process time: 30 to 120 sec

Other Embodiments

As described above, with the conventional plasma modifying method, acoating having uniform composition is formed and thereafter modified byirradiation with a plasma or the like.

In contrast to this, according to the present invention, when forming acoating layer, the densities of O atoms, N atoms, and the like arechanged to control the atomic densities freely. According to the presentinvention, for example, the gradients and distributions of the atomicdensities in the coating layer can be formed easily, and layers havingdifferent compositions can be stacked.

For example, in the present invention, when an organic film which hasbeen formed by [Spin on] while performing an N radical process isnitrided at 100° C., CN(sp³) can be formed easily. In the presentinvention, when an organic film is nitrided at 20° C., CN(sp²) can beformed easily. The etching resistance largely differs between sp³(difficult to etch) and sp² (easy to etch). Thus, the sp² component canbe selectively etched by utilizing sp³ and sp² film formation. With thisprocess, a porous low-dielectric-constant thin film (k≦2.0), the filmstructure of which comprises the sp³ component, can be formed.

As described above, in formation of a coating film in accordance withthe sol-gel method, when the plasma process according to the presentinvention is performed, a Bi—Ti—O film or the like (BIT) and a—Sr—Bi—Ta—O film or the like (SBT), each of which has a smooth surfaceand excellent crystal orientation and a leak current from which issmall, can be obtained easily.

FIG. 28 shows an example of a surface processing apparatus according tostill another embodiment of the present invention. In the apparatusshown in FIG. 28, NF₃ is used as an etching gas, and H₂O is used as aliquid. H₂O is obtained by bubbling He gas. How to obtain H₂O is notlimited to a bubbling means but a vaporizer can be used. Also, H₂O maybe obtained by direct liquid injection. An oxide film (SiO₂) is formedon the base material. The formed oxide film is etched efficiently. Whenthe process is performed by using this apparatus system, a high-qualitythin film can be formed and a surface process can be performed.

FIG. 29 shows still another embodiment of the present invention. In thisembodiment, the sol-gel method is employed to form Ferraelectic randomaccess meweries (FeRAMs).

Generally, in FIG. 29, a sol-gel solution (e.g., an alcohol cultureliquid or the like containing 10% weights of BSO, BIT, and SBT) can beintroduced to a reaction chamber to coat a Pt electrode (not shown) on awafer (electronic device base material) 112 with a thin film of Bi₂SiO₅(BSO), Pb(Zr, Ti)O₃(PZT), SrBi₂Ta₂O₉ (SBT), and Bi₄Ti₃O₁₂ (BIT).

In the above coating, when these solutions are introduced, a plasma of agas such as O₂ or Ar is generated simultaneously to deposit the thinfilm while irradiating the solutions or wafer with radicals and ionssuch as O⁻, O⁺, or Ar⁺. As a result, a dense thin film which has asmooth surface and excellent crystal orientation and which is free fromoxygen lack can be formed.

Furthermore, in FIG. 29, a supply unit 180 portion can be connected tothe apparatus, CO₂ which is pressurized (73 atm) at 31° C. can be set inthe supercritical state, and a solution mixed with BSO, PZT, SBT, andBTT can be introduced into the supercritical CO₂ solution to form a thinfilm while irradiating the solution with a plasma (regarding the detailsof such combination of the sol-gel method and supercriticality, forexample, e.g., Jpn. J, Appl. Phys. Vol 42 (2003), pp L404-L405 can bereferred to).

When an 80-nm thick BSO/BTT or SBT film was annealed at about 700° C.for 30 min, it showed excellent characteristics with a leak current onthe order of 10⁻⁵ A/cm².

This is because the thin film became dense and oxygen lack disappearedwhen the film was irradiated with O radicals, O⁻ ions, O⁺ ions, and Ar⁺ions generated by the atmospheric-pressure plasma.

A case will be described hereinafter wherein the plasma source andplasma processing apparatus according to the present invention areapplied to formation of carbon nanotubes.

A CNT (Carbon NanoTube) is a high-aspect-ratio hollow cylindricalcrystal having, e.g., a diameter of about several nm and a length ofabout 1 μm.

The physical properties of the CNT have been analyzed considerably inthe past several years. Currently, application of the CNT in very widefields is regarded promising, including the composite material field(e.g., for reinforcement and imparting conductivity) represented by anelectronic material, the electronics field (e.g., a transistor, diode,and wiring), an electron source (e.g., a field emission type electronsource, various types of displays), nanotechnology (e.g., probing with ascanning probe microscope (SPM), and nanomechatronics elements), theenergy field (e.g., hydrogen occlusion, an electrode or capacitormaterial), the chemical field in general (e.g., a gas sensor, catalyst,and organic raw material). Application of the CNT in some of the abovefields is already on the stage of practical use.

As a CNT manufacturing method, conventionally, the carbon arc dischargemethod, the carbon laser vaporization method, the hydrocarbon gasthermal decomposition method, the plasma CVD (Chemical Vapor Deposition)method, and the like which use acetylene gas or the like as the carbonsource are known. Above all, the plasma CVD method is advantageous interms of selective generation (Gekkan FPD Intelligence 1999. 11 P38-P40“Nippon Shinku develops CVD device for forming FED carbon nanotube whichvertically deposits carbon nanotube selectively”).

In CNT formation with the conventional plasma CVD method, the conditionrange for forming a good CNT is rather narrow. Accordingly, depending onthe characteristics or the like of the plasma to be used, frequently, aCNT having a good structure cannot be obtained.

In contrast to this, with the plasma source and plasma processingapparatus according to the present invention, a CNT having a good filmquality can be obtained.

(CNT Formation Process)

According to the present invention, as the CNT formation process, thefollowing three types can be employed.

(1) Plasma process; (2) Radical Process; and (3) Radical-emphasizedplasma process: of the above processes, when the “plasma process” isemployed, a sheath is formed in the plasma between the substrate surfaceand the plasma, and a CNT tends to grow toward an electrical fieldgenerated in the sheath. Accordingly, a CNT is generated even where itis not necessary. Sometimes a post-process is required to remove such anunwanted CNT.

When the radical process is employed, while applying an electrical fieldbetween predetermined electrodes (metals), a substrate is selectivelyirradiated with radical molecules or atoms by changing the type andenergy. A CNT can be selectively grown by these reactions.

When the radical process or radical-emphasized plasma process describedabove is to be employed, in order to selectively irradiate the substratewith the radicals, a porous hollow cathode discharge type plasma sourcedescribed with reference to FIGS. 1 to 4 can be used. Also, the“extracting electrode” is removed. Thus, the plasma source can be usedas a radical radiation source.

When the apparatus shown in FIGS. 1 to 4 is used for CNT formation, aheater or the like is set in the base material holding means 11 so thatthe target object placed on the base material holding means 11 can beheated to about 600° C.

(Gas)

The gas to be supplied into the chamber 2 is not particularly limited asfar as it can form an CNT, and various types of gases can be used inaccordance with the use of the CNT to be formed. More specifically,usually, various types of inert gases (e.g., a rare gas) can be used asa plasma formation gas, and various types of carbon-containing gases(e.g., acetylene) can be used as a CNT formation gas. Other gases may beadded when necessary. The gas that can be suitably used in the presentinvention will be described hereinafter.

Plasma generation gas: inert gas

Carbon-containing gas: CH-based gas

A CNT may also be formed by using the plasma processing apparatus shownin FIG. 30. In the plasma processing apparatus shown in FIG. 30, inorder that discharge readily focuses on electrode holes 3, dielectricporous spacers 4 a are arranged on the uppermost portion of a hollowcathode electrode member 4 as well. This also applies to the arrangementshown in FIGS. 26 and 27.

(Plasma Generation Principle)

In CNT formation using the plasma processing apparatus described above,the plasma generation principle is not particularly limited as far asplasma generation in the electrode holes 3 is possible. Morespecifically, in the embodiment shown in FIG. 1 described above, a DCvoltage is applied between each pair of porous conductor members 4 b.The DC voltage can be replaced by a high frequency or microwaves.

(Base Material)

In CNT formation using the plasma processing apparatus described above,various types of base materials (e.g., an electronic device basematerial such as a wafer) can be processed with a plasma. The basematerial is not particularly limited, and one type or a combination oftwo or more types of known base materials can be appropriatelyselectively used. An example of such a base material includes asemiconductor material and liquid crystal device material. An example ofthe semiconductor material includes a material containing single-crystalsilicon as a major component, e.g., SiC or GaAs.

(CNT Formation Method)

In the CNT formation method according to the present invention, whileirradiating a base material arranged in a process chamber with a plasma,a CNT formation material is supplied onto the base material to form aCNT layer on the base material.

(On Base Material)

In the present invention, a state “on the base material” is sufficientlyestablished as far as the CNT to be formed is located above the basematerial (that is, above that side of the base material where respectivelayers which constitute the electronic device are formed). In otherwords, another insulating layer, conductor layer, semiconductor layer,or the like may be arranged between the machinery and the CNT to beformed. Naturally, a plurality of various types of insulating layers,conductor layers, semiconductor layers, or the like including the CNT tobe formed in the present invention may be arranged when necessary.

(Thickness)

The thickness of the CNT layer to be formed in the present invention isnot particularly limited, but about several 1 nm (in the case of channelformation) to 2 (in the case of a wiring) is preferable.

As described above, according to the present invention, a CNT can beeasily formed between metals (e.g., electrodes). The metals that can beused are preferably transition metals from the viewpoint of the catalystfunction. Alternatively, an electrode obtained by dispersing atransition metal (Ni, Co, Pd, or the like) powder on the metal surface,or an electrode formed by selective position control is desirable.

According to the present invention, in addition to the method describedabove, a carbon nanocoil can be formed by using a NiFe catalyst (fordetails of formation of such a carbon nanocoil or CNT formation, forexample, Diamond and Related Materials, 9 (2000), 847-851; Dengakuron A,volume 118, No. 12 (year of Heisei 10) pp. 1425-1428 can be referredto).

(Example of Suitable Condition)

In the present invention, for example, the following conditions can besuitably used.

Microwaves: 2 kW/cm² (a DC voltage may be supplied to the hollow cathodeplasma source) 1 to 10 W/cm²

Gas: Ar, 1,000 sccm+H₂, 100 sccm, or Kr or He, 1,000 sccm+H₂, 100 sccm

Pressure: 1 to 760 Torr (133 to 10×10⁴ Pa)

Base material temperature: 500±50° C.

Process time: 60 to 600 sec

Other Embodiments

A hole that forms a microcathode is comparatively thin. Therefore, whenacetylene is supplied to the hole from above, contamination caused bysputtering or the like tends to occur readily in the microcathode. Inthis case, preferably, for example, H₂ gas may be supplied together withan inert gas (e.g., krypton) from the upper portion of the plasmasource, and acetylene (C₂H₂), methane gas, or the like may be suppliedfrom the lower portion of the plasma source, to form a CNT in themicrocathode. Furthermore, in order to form a catalyst site for the CNTgrowth, a gas containing a transition metal such as Ni, Fe, or Co, e.g.,Ni(CO)₄ or an organic metal gas, may be introduced from below the plasmasource.

In order to grow the CNT, a portion added with a catalyst (catalystsite) is often necessary. How to form the catalyst site in the presentinvention is not particularly limited, and a catalyst site can be formedfrom, e.g., nickel (for details of catalyst site formation, for example,J. Appl. Phys. 92 6188 (2003) can be referred to).

CNT formation can also be performed by using the apparatuses shown inFIGS. 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, and 21 describedabove.

For example, when the apparatus shown in FIG. 10 is to be used, voltagescan be applied to the respective pairs of electrodes of thethree-dimensional multiarray electrodes independently of each other. Inthe chamber of the plasma processing apparatus which uses a plasmasource formed of multiarray electrodes, a sample having athree-dimensional shape is set on the susceptor. A sample having a two-or three-dimensional shape can be processed with a plasma, chargedparticles, or radicals in accordance with the sample shape (not onlytwo-dimensionally but also three-dimensionally), as shown in, e.g.,FIGS. 31 and 32, by controlling the power supply appropriately by FDD.

Practical examples of CNT formation will be described hereinafter.

For example, any one of the various apparatuses described above is used.As the gas (A), H₂/Xe gas is introduced under the atmospheric pressurefrom above the multielectrodes.

Evacuation is performed through the multielectrodes to maintain thepressure in the lower reaction chamber at about 10 Torr. CH₄/H₂ orC₂H₂/H₂ gas is introduced from the lower electrode to grow a CNT on anSi substrate (SiO₂/Si) substrate obtained by depositing Ni on an SiO2film. The substrate temperature is set to 600° C. The substrate is usedas the sample the distance between the multielectrodes and the sample isabout 10 mm.

In the multielectrodes, a large amount of H radicals are generated bythe reaction of H₂+e→H+H, He+e→He⁺+e+e and introduced into the reactionchamber. The substrate is irradiated with high-speed H radicals with anenergy of about 5 eV or less in the same manner as in Example 1.

The interaction of the high-speed H radicals and CH₃ or C₂ radicalsforms a CNT on the substrate. With this method, both the H radicaldensity and the density of C₂ or the like become high, and the two typesof radicals can be controlled independently of each other. Consequently,a CNT film free from any defect can be formed at a high speed.

Furthermore, as shown in FIG. 33, when high-frequency power of 100 MHzis applied between the lowermost electrode of the multielectrodes andthe substrate electrode 2, a capacitively coupled gas plasma of CH₄/H₂or C₂H₂/H₂ or a gas plasma obtained by adding a gas containing Ni or thelike to a gas mixture of CH₄/H₂ and C₂H₂/H₂, which is excited at 100MHz, can be applied, and high-density H radicals can be inserted in theplasma.

INDUSTRIAL APPLICABILITY

The present invention can be applied to a processing apparatus such as aplasma CVD apparatus or etching apparatus. The process need not be onewhich uses a plasma, but the present invention can also be applied to,e.g., catalyst CVD. Furthermore, the process need not use a gas, but thepresent invention can also be applied to, e.g., sputtering.

1. A plasma source characterized by comprising at least: a chamber towhich a gas should be supplied; and a hollow cathode electrode memberwhich is arranged on a gas flow-out side of said chamber and has aplurality of electrode holes through which the gas can flow, whereinsaid hollow cathode electrode comprises pairs of porous conductormembers which are combined through dielectric porous spacers, andmicrocathode plasma discharge is performed in the electrode holes ofsaid hollow cathode electrode member.
 2. (canceled)
 3. A plasma sourceaccording to claim 1, comprising an extracting electrode correspondingto said hollow cathode electrode, wherein said extracting electrode hasa hole through which a plasma is to penetrate.
 4. A plasma sourceaccording to claim 1, wherein said hollow cathode electrodes comprise amultistage electrode including not less than three stages.
 5. A plasmasource according to claim 1, wherein said hollow cathode electrodescomprise a three-dimensional electrode.
 6. A plasma source according toclaim 5, wherein said three-dimensional electrode comprises an electrodein which individual hollow cathode electrodes can be controlledindependently of each other.
 7. A plasma source according to claim 1,wherein a potential to be applied to said hollow cathode electrode canchange over time.
 8. A plasma processing apparatus characterized bycomprising: a process chamber; base material holding means for arranginga base material at a predetermined position in said process chamber; anda plasma source to selectively irradiate a base material with at leastone of a plasma, charged particle, and radical, wherein said plasmasource includes at least a chamber to which a gas should be supplied;and a hollow cathode electrode member which is arranged on a gasflow-out side of said chamber and has a plurality of electrode holesthrough which the gas can flow, and said hollow cathode electrodecomprises pairs of porous conductor members which are combined throughdielectric porous spaces, and microcathode plasma discharge is performedin the electrode holes of said hollow cathode electrode member.
 9. Aplasma processing apparatus according to claim 8, wherein the basematerial comprises any one of an electron device base material, opticaldevice base material, and bio-device base material.
 10. A plasmaprocessing apparatus according to claim 8, wherein said plasma sourcecomprises an atmospheric-pressure plasma source.
 11. A plasma processingapparatus according to claim 8, wherein a gas is supplied into saidprocess chamber.
 12. A plasma processing apparatus according to claim 8,wherein any one of an atmospheric-pressure plasma and reduced-pressureplasma is generated in said process chamber.
 13. A plasma processingapparatus according to claim 8, wherein a voltage to be applied to saidhollow cathode electrode is changed to irradiate the base material withnot less than one type of active species selected from the groupconsisting of an ion, electron, and radical.
 14. A plasma processingapparatus according to claim 8, characterized by comprising: basematerial holding-means for arranging a base material at a predeterminedposition in said process chamber; and coating material supply means forsupplying a coating material, wherein the base material is irradiatedwith at least one of a plasma, neutral radical, and positive/negativeion by said plasma source, and while the base material is irradiatedwith at least one of the plasma, neutral radical, and positive/negativeion, a coating layer formed of the coating material is formed on thebase material.
 15. A plasma processing apparatus according to claim 14,wherein said plasma source comprises a plasma source including a slitand microwave supply means for supplying microwaves to the slit.
 16. Aplasma processing apparatus according to claim 14, wherein the coatinglayer is formed by spin coating.
 17. A plasma processing apparatusaccording to claim 14, characterized in that while the base material isirradiated with at least one of the plasma, neutral radical, andpositive/negative ion, the coating material is supplied onto the basematerial to form the coating layer.
 18. A plasma processing apparatusaccording to claim 14, wherein a distance between a plasma radiationport of said plasma source and the base material to be processed withthe plasma is not more than 5 mm.
 19. A plasma processing apparatusaccording to claim 8, characterized by comprising: base material holdingmeans for arranging a base material at a predetermined position in saidprocess chamber; and carbon nanotube formation material supply means forsupplying a carbon nanotube formation material, wherein the basematerial is irradiated with at least one of the plasma, neutral radical,and positive/negative ion, and while the base material is irradiatedwith at least one of a plasma, neutral radical, and positive/negativeion, a carbon nanotube formation layer is formed on the base material.20. A plasma processing apparatus according to claim 19, characterizedin that while the base material is irradiated with at least one of theplasma, neutral radical, and positive/negative ion, the carbon nanotubeformation material is supplied onto the base material to form the carbonnanotube formation layer.